1. Field of the Invention
The present invention relates to a battery charger or booster and in particular to a high frequency charger.
2. Technical Background
Dual-mode battery chargers currently exist. When operated in a first mode, the battery charger delivers a high current output for a short duration of time. This short duration, high current can be used to jump-start a vehicle with a dead battery. In a second mode, the battery charger provides a low current output that is used to charge the battery back to its full charge. Known dual-mode battery chargers typically use a single large transformer to achieve the dual-mode capability. The single transformer is usually a linear type transformer. A tap of a primary winding of the transformer is changed in order to achieve the dual capability with the linear-type transformer. As the tap of the transformer is changed, the output voltage, and hence, according to Ohm""s Law, the output current of the transformer is changed, resulting in the dual-mode capability. Use of a single transformer for both modes of operation has the advantage of being very cost-efficient and very effective.
However, this approach also has several disadvantages. One of the disadvantages is that known single transformer battery chargers are very large and cumbersome. Standard linear transformers require iron for their cores, adding to the weight of the battery charger. They also require orders of magnitude more wire to form their windings than do high frequency chargers, again adding to the weight of the battery charger.
Additionally, although the linear transformer can provide a high current output, the high current output can only be provided for a very short period of time. As the transformer operates in high current mode, it generates an excessive amount of heat. In fact, so much heat may be generated that the transformer actually melts down. If a meltdown occurs, the transformer will not operate in either the high current mode or the low current mode. Linear transformers are also very lossy in terms of magnetic losses and eddy current losses, resulting in inefficiency.
Further, to charge an automobile battery that is of insufficient electric power by providing power from another power source, like a battery charger, the power source and the battery must be connected through a pair of electric wires, typically having clamps at their ends for connection to the battery. Making this connection can be very dangerous if there is a problem with the connection. For example, it is well known that sparking or arcing often occurs when a connection is being attempted between a battery charger and a battery. Additionally, sparking or arcing may occur when the clamps are connected to the battery with a reverse polarity. Sparking or arcing can also occur even after an apparently good connection is made. The sparking or arcing may occur due to corroded or poor terminal connections.
In the past, the use of a delay circuit or xe2x80x9csoft startxe2x80x9d was used to prevent sparking. A delay circuit prevents power flow to the battery from occurring until a connection is made between the battery and the battery charger. This method helps to prevent sparking upon the initial connection of the battery and battery charger. However, it does not prevent any sparking that occurs as a result of poor or corroded connections, the existence of which can only be determined after current flow begins. Sparking or arcing may result in damage to the battery, and under certain circumstances, an explosion, fire and damage to the vehicle or to a person may result.
Additionally, a characteristic of liquid electrolyte type batteries, particularly lead acid batteries used in vehicles, is that chemical compound deposits slowly build up on the plates to partially or entirely cover and displace the normal, plate surfaces. Low current recharging is inadequate in that it can not, as such, sufficiently remove such deposits that with the passage of time crystallize and choke the battery plates by interfering with electrolyte movement. When this occurs a battery may still appear to have taken a charge and even the electrolyte may check as being correct, but the battery does not hold the charge because the plates are effectively shorted. Batteries using other electrolytes also face reclaiming, maintenance and charging problems that need to be successfully addressed.
Thus, there is a need for a method to release the deposits that are built up on the plate surfaces, where the deposits may either go back into the solution or be broken up. There is also a need for a simple and lightweight dual-mode battery charger. The battery charger should be able to provide a high current output that is sufficient to start an automobile or other vehicle with a dead battery, yet be easy to construct and safe to operate.
Definitions:
In describing the invention, the following definitions are applicable throughout this application.
A xe2x80x9ccomputerxe2x80x9d refers to any apparatus that is capable of accepting a structured input, processing the structured input according to prescribed rules, and producing results of the processing as output. Examples of a computer include a computer; a general-purpose computer; a supercomputer; a mainframe; a super mini-computer; a mini-computer; a workstation; a microcomputer; a processor; a server; an interactive television; a hybrid combination of a computer and an interactive television; and application-specific hardware to emulate a computer and/or software. A computer can have a single processor or multiple processors, which can operate in parallel and/or not in parallel. A computer also refers to two or more computers connected together via a network for transmitting or receiving information between the computers. An example of such a computer includes a distributed computer system for processing information via computers linked by a network.
A xe2x80x9ccomputer-readable mediumxe2x80x9d refers to any storage device used for storing data accessible by a computer. Examples of a computer-readable medium include a magnetic hard disk; a floppy disk; an optical disk, like a CD-ROM or a DVD; a magnetic tape; a memory chip (e.g., ROM or RAM); and a carrier wave used to carry computer-readable electronic data, such as those used in transmitting and receiving e-mail or in accessing a network.
xe2x80x9cSoftwarexe2x80x9d refers to prescribed rules to operate a computer. Examples of software include software; code segments; instructions; computer programs; and programmed logic.
A xe2x80x9ccomputer systemxe2x80x9d refers to a system having a computer, where the computer comprises a computer-readable medium embodying software to operate the computer.
According to an embodiment of the invention, a high frequency charger for charging a battery is provided. The charger comprises a charge circuit including a first high frequency transformer. A first switch switches the first high frequency transformer at a first frequency. The charger also includes means for measuring a charge rate of the battery; means for determining an amount of time the battery has been charging; means for measuring a voltage of the battery; and means for detecting an overtime fault if the charge rate is greater than a predetermined current, the battery has been charging longer than a predetermined amount of time, and the voltage of the battery is greater than or equal to a predetermined voltage.
In another embodiment, the high frequency charger comprises: a charge circuit including a first high frequency transformer; a first switch switching the first high frequency transformer at a first frequency; means for measuring a charge rate of the battery; means for determining an amount of time the battery has been charging; means for measuring a voltage of the battery; and means for detecting a shorted cell battery fault if the charge rate is greater than a predetermined current, the battery has been charging more a predetermined amount of time, and the voltage of the battery is less than or equal to a predetermined voltage.
In another embodiment, the high frequency charger for charging a battery comprises a charge circuit including a first high frequency transformer; a first switch switching the first high frequency transformer at a first frequency; clamps for connecting the charger to the battery; means for measuring a voltage at the clamps; means for indicated a bad battery fault if no voltage is detected at the clamps.
In another embodiment, the high frequency charger comprises a charge circuit including a first high frequency transformer; a first switch switching the first high frequency transformer at a first frequency; means for measuring a charge current of the battery; means for determining an amount of time the battery has been charging; means for measuring a voltage of the battery; and means for detecting an open cell battery fault if the charge current is less than a predetermined current, the battery has been charging more a predetermined amount of time, and the voltage of the battery is greater than or equal to a predetermined voltage.
According to an embodiment of the invention, there is provided a high frequency charger that includes a charge circuit and a boost circuit. In a preferred embodiment, the charge circuit includes a first high frequency transformer. A switch switches this first high frequency transformer at a predetermined frequency. The boost circuit includes a second high frequency transformer that is separate from the first high frequency transformer in the charge circuit. The first and second high frequency transformers are operated in a similar manner. However, the boost circuit is adapted provide a high current that can be used to jump-start a vehicle with a depleted battery.
According to a variation on the preceding embodiment of the invention, there is provided a high frequency charger that includes a charge circuit and a boost circuit. In this embodiment, the charge circuit and the boost circuit are constructed using a single high frequency transformer having two windings on its primary side, a charge winding and a boost winding. The charge winding and the boost winding effectively form (along with the single secondary winding) the first and second high frequency transformers of the preceding embodiment of the invention (and may thus be thought of as the two separate transformers in other embodiments of the invention). The boost winding is adapted to provide a high current that can be used to jump-start a vehicle with a depleted battery.
In a preferred embodiment, a PWM controller provides a driving signal to the switch such that the transformer of the charge circuit is switched to output a pulse. The pulse output of the charge circuit can be used to condition the battery.
As noted, the transformer in the charge circuit and the transformer in the boost circuit are preferably separate from each other, that is, there are two transformers and associated circuits. Thus, the battery charger is not dependent on the same transformer for both standard charging and boosting. For example, if the transformer in a conventional charger burns out while performing a boost function, all the functionality of the charger may be lost, as one transformer is used for both functions. However, in the present embodiment, either of the transformers still operates even if the other transformer is disabled for some reason.
A control circuit for a high frequency charger is also provided. In an exemplary embodiment, the control circuit includes a pulse width modulation (PWM) controller having a reference voltage input, a control input, and an output for a control signal. A switch receives the control signal and is switched on and off in response to the control signal. A voltage divider network divides the voltage applied to the reference voltage input and the control input. A duty cycle of the control signal output from the PWM controller varies based on the percentage of the reference voltage that is applied to the control.
In a further embodiment, the voltage divider network comprises a first resistor having a first terminal connected to the reference voltage input and a second terminal connected to the control input. A plurality of second resistors each has a first terminal connected to the second terminal of the first resistor and a second terminal. A plurality of transistors are also provided, each having a first electrode connected to the second terminal of one of the second resistors, a second electrode that is grounded, and a third electrode receiving an enable signal. The enable signal turns the transistors on and off, selectively connecting one of the second resistors to ground.
In another embodiment, a method for reducing arcing in a battery charger comprises: providing a test current that is lower than a charging current from the battery charger to a battery; detecting if the test current is present at the battery; if the test current is not detected at the battery, indicating a fault; and if the test current is detected at the battery, increasing the test current a predetermined amount and returning to the detecting step.
According to another aspect of the invention there is provided a computer-readable storage medium for use with a computer for controlling a high frequency charger including a charge circuit having a first high frequency transformer; a first switch switching the first high frequency transformer at a predetermined frequency for producing a charge signal in a first mode of operation; the charge circuit operating in at least one of a pulse mode and a charge mode; and a selector for selecting one of the charge mode and the pulse mode, the computer-readable information storage medium storing computer-readable program code for causing the computer to perform the steps of: detecting a selected mode of operation for the charger; and when a pulse mode is selected, a) generating a driving signal for the first switch for a first period of time; b) disabling the first switch for a second period of time; and c) returning to step a).
According to yet a further aspect of the invention, there is provided a computer-readable information storage medium for use with a computer controlling a high frequency charger comprising a charge circuit including a high frequency transformer; and a switch switching the high frequency transformer at a predetermined frequency, the computer-readable information storage medium storing computer-readable program code for causing the computer to perform the steps of: checking a flag indicating the battery is in a bulk charge state or an absorption charge state; if the battery is in the bulk charge state, increasing a duty cycle of a driving signal for the first switch if a current provided by the battery charger is less than a desired current; decreasing the duty cycle of the driving signal for the first switch if a current provided by the battery charger is greater than the desired current; setting the flag indicating the battery is in the absorption charge stage when a voltage of the battery is greater than or equal a predetermined voltage and has been charging for a predetermined period of time, otherwise ending the charging process; if the battery is in the absorption charge stage, decreasing the duty cycle of the driving signal for the first switch if the voltage of the battery is greater than or equal to a predetermined voltage; increasing the duty cycle of the driving signal for the first switch if the voltage of the battery is less than the predetermined voltage; and stopping the charging process when the battery has been charging for more than a predetermined time.
According to yet another embodiment of the invention, computer-readable information storage medium for use with a computer controlling a high frequency charger comprising a charge circuit including a first high frequency transformer; a first switch switching the first high frequency transformer at a first frequency; a boost circuit including a second high frequency transformer; a second switch switching the second high frequency transformer at a second frequency, and a selector for selecting one of a charge mode for charging a depleted battery and a boost mode for supplying a boosting current to start a vehicle with the depleted battery, the computer-readable information storage medium storing computer-readable program code for causing the computer to perform the steps of: detecting a selected mode of operation; if the boost mode is selected, controlling the boost circuit to supplying a boosting current to the depleted battery; checking for a rapid rise in voltage after the vehicle has been started; if the rapid rise in voltage is present, indicating the alternator is working properly; and if the rapid rise in voltage is not present, indicating the alternator is not working properly.
According to yet another embodiment of the invention, a high frequency charger for charging a battery, comprises a charge circuit including a first high frequency transformer; a first switch switching the first high frequency transformer at a first frequency; a filter coupled to the first and second high frequency transformers for passing a DC voltage signal; means for coupling a resistance in parallel with the battery; means for measuring a voltage of the battery while the battery is coupled to the resistance; and means for correlating the measured voltage to a CCA value.
The above and other features of the invention, along with attendant benefits and advantages will become apparent from the following detailed description when considered with the accompanying drawings.